Abstract 797: Obesity-associated, but not obesity-independent, tumors respond to insulin by increasing mitochondrial glucose oxidation

Abstract

Abstract Obesity is associated with increased incidence and worse prognosis of more than one dozen tumor types; however, the molecular mechanisms for this association are unknown. We hypothesized that insulin, which is elevated in obesity-driven insulin resistance, would increase tumor glucose oxidation in obesity-associated tumors. To test this hypothesis, we developed a stable isotope method in which tumor cells are incubated in physiological concentrations (5 mM) of [13C6] glucose and the ratio of pyruvate dehydrogenase flux to citrate synthase flux (VPDH/VCS, i.e. the percent of total mitochondrial oxidation fueled by glucose oxidation) is given as [4,5-13C2]glutamate/[13C3]alanine, measured by gas chromatography/mass spectrometry and liquid chromatography-tandem mass spectrometry respectively. Using this method, we found that both breast cancer (4T1) and colon cancer (MC38) cells, tumors that are associated with obesity, exhibit greater relative rates of glucose oxidation to total mitochondrial oxidation (VPDH/VCS 61±3% and 60±2%, respectively) than melanoma (YUMM) and Renca (renal cell carcinoma) cells (41±4% and 37±2%, respectively; P<0.05 for all comparisons between obesity-associated and non-obesity-associated tumors). In addition, both 4T1 and MC38 cells increased VPDH/VCS upon incubation in 100 nM insulin (75±3% and 81±2%, respectively, P<0.01 vs. the same tumor type without insulin), whereas there was no change in glucose oxidation with insulin in YUMM or Renca cells (35±3% and 36±2%, respectively). These data reveal that a shift in substrate preference may comprise a metabolic signature of obesity-associated tumors that differs from that of those not associated with obesity. In addition, contrary to the conventionally held view that glucose oxidation in tumor cells is constitutively high, these data reveal that obesity-driven tumors respond acutely to insulin by increasing mitochondrial glucose oxidation, whereas obesity-independent tumor cells do not. CONCLUSION: These data demonstrate that obesity associated tumors (breast and colon), in contrast to tumors that are not associated with obesity (melanoma, renal cell), are insulin-responsive and have higher rates of basal and insulin-stimulated mitochondrial glucose oxidation. Therefore assessment of in vitro tumor mitochondrial substrate preference may predict whether interventions to reverse hyperinsulinemia or reduce insulin-responsive glucose oxidation in tumors may be attractive therapeutic modalities in cancer types associated with obesity. Citation Format: Aviva Rabin-Court, Gerald I. Shulman, Rachel J. Perry. Obesity-associated, but not obesity-independent, tumors respond to insulin by increasing mitochondrial glucose oxidation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 797.